Lift

Lift
With the ageing of the population more people are considering lifts in their houses.
While many are actually installing lifts others are creating the space in which
a lift can be added at some later date. 

Observation lifts have glass sides so that passengers can view their surroundings. These lifts are installed in interior courts or along exterior walls.

A Hydraulic lift is lifted and lowered by a ram (piston). The car rises when a pump forces oil into the ram cylinder. The car descends when the oil flows into a storage tank.

A gearless traction lift, has steel cables called hoisting ropes that fit around a sheave. When the sheave is turned by an electric motor, the ropes lift or lower the car.

The first lift with a safety device was demonstrated by Elisha G. Otis in 1854. The automatic device prevented the lift from fall­ing if the hoisting rope broke.

Lift is a transportation device that carries people and freight to the floors of a building. The word lift usually means the car in which the people or freight travel. But the term also refers to the entire system that controls the car's movement. The car travels up and down in a shaft that has steel guide rails to prevent movement sideways. In the United States, a lift is called an elevator.

The development of lifts led to the construction of skyscrapers. Lifts enabled architects to design taller and taller buildings because people no longer had to climb stairs to reach the upper floors.

Passenger lifts and freight lifts operate in many places and serve a variety of purposes. The passenger lifts commonly seen in office and residential buildings can carry from 900 to 1,800 kilograms. Some freight lifts can carry as much as 45,000 kilograms.

There are more than 2 million lifts in the world, and about 390,000 of them are in the United States and Can­ada. Lifts in the United States and Canada carry a total of about 350 million passengers daily.

How lifts work. Most lifts operate automatically. Only a few are run by attendants who ride in the cars. A person brings a lift to a certain floor by pushing a but­ton in the wall outside the shaft. The lift doors open au­tomatically after the car arrives at the floor, and they close after the passenger has entered. The passenger pushes a button to indicate the floor where he or she wants the lift to stop. The car stops at all floors where passengers want to be picked up or wish to get out.

Most lifts in buildings of 10 or more floors are pow­ered by electric traction systems and are lifted by steel cables. There are two types of electric traction lifts, gearless traction and geared traction.

Gearless traction lifts are used in office buildings of more than 10 floors and in residential buildings of more than 30 floors. They travel at speeds of 120 to 600 metres per minute. Cables called hoisting ropes lift the car. One end of each cable is attached to the top of the car. The other end is connected to a heavy steel counterweight that balances the weight of the car and about half of its maximum passenger load. The counterweight reduces to a minimum the power needed to operate the lift. The hoisting ropes fit around a sheave (pulley) that is con­nected directly to an electric motor.

As the sheave turns, the ropes move and the car goes up or down. A brake holds the car in place when the lift stops.

Geared traction lifts travel at speeds as high as 137 metres per minute. Geared traction lifts are similar to the gearless traction type of lift. However, the motor of a geared traction lift operates a reduction gear, which turns the sheave. This gear decreases the speed at which the sheave would otherwise turn.

Some lifts, called hydraulic lifts, are driven by a hy­draulic system. They are lifted and lowered by a long ram (piston) instead of by steel cables. Such lifts travel at speeds of 15 to 48 metres per minute. They serve many buildings of six or fewer storeys. The ram rises and lifts the lift when an electric pump forces oil into the ram cylinder. The lift goes down when a valve opens and the oil flows into a storage tank.

Safety features. In many countries, lifts must operate according to safety codes, normally defined by an or­ganization of agencies, including consumer, govern­ment, and industrial groups. Officials then inspect the lifts regularly to make sure that all the safety features are functioning.

Passenger lifts are usually expected to have steel doors that can withstand fire. Most lifts have two sets of doors. One set is in the walls at each floor, and the other set is part of the car itself. Both sets of doors must close  and lock before the lift can move. A special safety device causes the doors to reopen if someone is in the doorway. If a lift goes too fast as it travels down, safety clamps grab the guide rails and stop the car. All auto­matic lifts have alarm bells, and some have intercom systems or telephones. Passengers can use these instru­ments in emergencies, such as to call for help if the lift stops between floors.

Special kinds of lifts. Some large buildings have double-deck lifts, which have two compartments and serve two floors with each stop. People who want to go to odd-numbered floors enter the lower compartment of the lift on the first floor. Those people who want even-numbered floors enter on the second floor and ride the upper compartment. Lifts called observation lifts glass sides and travel along the walls of interior courts or along the outside walls of buildings. Passengers can view the surrounding area through the glass sides.

Some tall buildings have express lifts that travel non-stop to certain floors where passengers change to local lift. The local lifts then carry the people to their floors. Construction companies use lifts that travel along the outside of buildings and carry crews and building materials. Other kinds of lifts take workers and materials into mines. Hospital lifts are large enough to carry beds and stretches.

History. The ancient Greek mathematician Archimedes invented a type of lift before 230 B.G It used ropes and pulleys and could lift one person.

lifts were in use during the early 1800’s. By the 1840's, both hydraulic and steam-powered freight lifts had been invented. But the hydraulic lifts were very slow, and the ropes of the steam-powered lifts often broke and the cars fell.

In the early 1850's an American, Elisha G. Otis, invented the first lift that had an automatic safety device. If the rope broke, the device prevented the lift from falling.

Otis first demonstrated the lift in 1854. The world's first lift designed specifically for passenger use was in­stalled in New York City in 1857. The world's first electric lift started operating in 1889.

Automatic lifts were introduced in residential build­ings in the 1890's. Attendants operated the lifts in major office buildings until 1950. That year, an office building in Dallas, Texas, U.S.A., became the first to have auto­matic lifts. See also Elisha G. Otis